1. Field of the Invention
The present invention relates to a cathode ray tube, and more particularly, to a funnel structure of a cathode ray tube in an optimum funnel horn shape that is capable of improving a sensitivity of a deflection yoke and capable of satisfying a beam shadow neck margin of an electron beam.
2. Description of the Background Art
As shown in FIG. 1, a conventional cathode ray tube includes a fluorescent face 4 is formed with R (red), G (green) and B (blue) fluorescent material coated thereon, a panel 1 formed at a front portion with an explosion-proof unit fixed thereon, a funnel 2 melt at a rear end of the panel 1, an electron gun (no reference numeral given) inserted into a neck portion 13 of the funnel 2 and emitting electron beam 6, a deflection yoke 5 for deflecting the electron beam 6, a shadow mask 3 mounted to have a certain interval with an inner face of the panel 1 and having a plurality of holes for passing the electron beam 6, a main frame 7 and a sub-frame 8 fixedly supporting the shadow mask 3 so that the shadow mask 3 can be maintained with a certain interval with the inner face of the panel 1, a corner spring 9 for connecting and supporting the main frame 7 and the panel 1, an inner shield 10 for shielding the cathode ray tube so that the cathode ray tube can be less influenced by an external earth magnetism, and a reinforcing band 12 installed around the side portion of the panel 1 and preventing an external impact.
A magnet 11 made of 2, 4 and 6 poles is provided to correct a proceeding trajectory of the electron beam so that the electron beam can accurately hit the fluorescent material is provided, by which a color purity defect can be prevented.
A rug 14 is welded at a corner portion of the reinforcing band 12 and coupled with an outer case of a television set or a monitor.
The overall fabrication process of the CRT can be divided into a former process and a latter process. In the former process, step of coating the fluorescent face 4 onto the inner surface of the panel 1, while the latter process includes the following several steps.
First, the fluorescent face 4 is formed, and the panel 1 having a mask assembly in which the shadow mask 3 and the frames 7 and 8 are coupled inserted therein and the funnel 2 having a sealing face with a frit glass coated thereon are sealed at a high temperature through an envelop process. Thereafter, the electron gun is inserted into the inner side of the neck portion 13 of the funnel 2 through an encapsulating process, and the inside of the CRT is vacuumized through an exhausting process and then enclosed.
When the inside of the CRT is vacuumized through these processes, the CRT is compressed or receives a tensile stress according to a shape of the CRT due to an atmosphere pressure.
If a surface area is reduced as a depth of the panel 1 or the funnel 2 becomes considerably small compared to that of the conventional art, the force applied per unit area is increased. Thus, there is shown such a stress distribution that a relatively high stress is concentrated thereto.
As a matter of course, after the exhausting process, the stress concentration occurring at the panel 1 and the funnel 2 can be distributed by attaching the reinforcing band 12 at an outer circumferential surface of the panel 1 so as to make an effect of reducing its absolute value. But such an effect is made little in case of a slim type CRT.
Meanwhile, as shown in FIG. 2, the funnel 2 of a general CRT is divided into a funnel body portion 2a, a funnel yoke portion 2b where the deflection yoke 5 is positioned, and a neck portion 2c where the electron gun is positioned.
A boundary line at which the funnel body portion 2a and the funnel yoke portion 2b meet is defined as a top of round 21, a boundary line at which the funnel yoke portion 2b and the neck portion 2c meet is defined as a neck seal line 23, and, a reference line, though not shown with an actual object but always defined in designing, in measuring a depth of the CRT is defined as a reference line 22.
Provided that a region of the screen actually shown is an effective screen and diagonal ends of the four corners of the effective screen are effective surface end 25, when the point at which the tube axis 24 and the reference line 22 intersect is connected to the effective surface end 25, an angle with the tube axis 24 is defined as a deflection angle 26.
The CRT is mainly used for a television set, a computer monitor, or the like, and recently, it is also applied to a high quality product such as an HDTV.
In order for the CRT to be applied to the high quality television or a monitor, or in order to improve a quality itself such as improvement of a brightness of the screen, a deflection frequency of the deflection yoke 5 needs to be heightened. In this respect, however, heightening of the deflection frequency causes problems that a leakage magnetic field is generated due to an increase in a deflection power and a power consumption is increased.
Meanwhile, when the CRT is adopted as a computer monitor, the leakage magnetic field leaked from the product is regulated by a related agency. If a compensation coil is mounted at the deflection yoke 5 in order to reduce the leakage magnetic field, the effect of reducing the leakage magnetic field may be expected to a degree but a power consumption is increased according to the use of the compensation coil which results in an increase in an expense.
And recently, as the CRT is in the trend toward being slim, a distance between the electron gun and the fluorescent material coated at the inner surface of the panel 1 becomes short, and accordingly, as the deflection angle of deflecting the electron beam 6 becomes large, a power consumption of the deflection yoke 5 for controlling the deflection angle is increased.
In an effort to solve the problem, these days, the funnel 2 to which the deflection yoke 5 is mounted has such an outer circumference shape that it is changed from a circular form to an oval form as it goes from the neck portion 2c of the funnel 2 toward the panel 1, or an almost rectangular funnel yoke portion 2b, not the circular funnel yoke portion 2b, is used so that a horizontal or vertical coil of a deflection coil (no reference numeral given) comes near the region where the electron beam 6 formed inside the funnel 2, thereby resultantly reducing power required for the deflection.
However, if the CRT is made slim, even though the rectangular yoke portion is used, the amount of increase in the deflection power is meager compared with the CRT with the existing deflection angle. In addition, due to the structural characteristics of the rectangular shape, the stress concentration is more severe to the diagonal portion of the rectangular yoke portion.
FIG. 3 is a sectional view of the funnel yoke portion 2b of the conventional art.
The deflection yoke 5 is attached to the funnel yoke portion 2b to control the electron beam 6 emitted from the electron gun to reach the fluorescent material coated at the inner surface of the panel 1. In this respect, if the rectangular yoke portion of the funnel 2 is designed to come closer to the tube axial direction in order to reduce the deflection power, the electron beam 6 collides with the inner surface of the funnel 2, causing a problem of a BSN phenomenon that it is shown black in an actual screen, as shown in FIG. 4.
Moreover, after the CRT is completely fabricated, there needs to be a margin of about 3xcx9c4 mm back and forth along the tube axis 24 of the CRT so as for the deflection yoke 5 to be movable for a screen adjustment such as an ITC. If there is no margin between the electron beam 6 and the inside of the funnel 2, the electron beam 6 would easily collide with the inside of the funnel 2.
The position with which the electron beam 6 collides differs depending on the deflection angle as designed in the CRT. If the deflection angle is small, as shown in FIG. 5A, the electron beam collides with the neck seal line 23 of the inner surface 31 of the yoke portion. Meanwhile, if the deflection angle is large, as shown in FIG. 5B, the electron beam collides with the inner surface 31 of the yoke portion at the side of the top of round 21.
The BSN phenomenon occurs according to the margin between the inner surface 31 of the yoke portion 2b and the electron beam passing region. If there is no margin, as shown in FIG. 6, a shadow is formed at the end 25 of the effective surface diagonal portion due to the BSN phenomenon.
Therefore, in consideration of the power consumption, preferably, the yoke portion 2b of the funnel 2 should be designed to be small so that it can come as close as possible to the electron beam 6. But in the aspect of implementation of an image without the BSN phenomenon, there is a limitation in designing to make the yoke portion 2b small.
Therefore, an object of the present invention is to provide a method for designing an optimum funnel yoke portion that is capable of reducing a deflection power in fabricating a slim type CRT and capable of obtaining a margin between an inner side of a funnel and an electron beam passing region without causing a BSN phenomenon.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a funnel structure of a cathode ray tube having a panel with a fluorescent screen inside thereof, a funnel sealed to the panel in a vacuum state, an electron gun mounted at a neck portion of the funnel and emitting an electron beam toward the fluorescent screen, and a deflection yoke mounted at a yoke portion of the funnel and deflecting the electron beam, wherein provided that a deflection angle is 110xc2x0 or more, a length of an outer surface evaluation line formed by connecting a TOR outer surface end where the funnel yoke portion and the funnel body portion meet and a neck seal outer surface end where the funnel yoke portion and the neck portion meet by a straight line is xe2x80x98axe2x80x99 and a length of a straight line from the outer surface evaluation line where a vertical distance between the funnel yoke portion outer surface and the outer surface evaluation line is maximized, to the neck seal outer surface end is xe2x80x98bxe2x80x99, a formula of 0.20xe2x89xa6b/axe2x89xa60.40 is satisfied.
To achieve the above objects, there is also provided a funnel structure of a cathode ray tube having a panel with a fluorescent screen inside thereof, a funnel sealed to the panel in a vacuum state, an electron gun mounted at a neck portion of the funnel and emitting an electron beam toward the fluorescent screen, and a deflection yoke mounted at a yoke portion of the funnel and deflecting the electron beam, wherein provided that a deflection angle is 110xc2x0 or more, a length of an outer surface evaluation line formed by connecting a TOR outer surface end where the funnel yoke portion and the funnel body portion meet and a neck seal outer surface end where the funnel yoke portion and the neck portion meet by a straight line is xe2x80x98axe2x80x99, a length of a straight line from the outer surface evaluation line where a vertical distance between the funnel yoke portion outer surface and the outer surface evaluation line is maximized, to the neck seal outer surface end is xe2x80x98bxe2x80x99, a length of a straight line from a point on an outer surface of the funnel yoke portion at which a vertical distance from the outer surface of the funnel yoke portion to the outer surface evaluation line xe2x80x98axe2x80x99 is maximized to the neck seal end is b1, an included angle between xe2x80x98bxe2x80x99 and xe2x80x98b1xe2x80x99 is xe2x80x98dxe2x80x99, and an angle formed by a tube axis and the outer surface evaluation line is xe2x80x98cxe2x80x99, a formula of 0.22xe2x89xa6d/cxe2x89xa60.42 is satisfied.
To achieve the above objects, there is also provided a funnel structure of a cathode ray tube having a panel with a fluorescent screen inside thereof, a funnel sealed to the panel in a vacuum state, an electron gun mounted at a neck portion of the funnel and emitting an electron beam toward the fluorescent screen, and a deflection yoke mounted at a yoke portion of the funnel and deflecting the electron beam, wherein provided that a deflection angle is 110xc2x0 or more, a length of an inner surface evaluation line formed by connecting a TOR inner surface end where the funnel yoke portion and the funnel body portion meet and a neck seal inner surface end where the funnel yoke portion and the neck portion meet by a straight line is xe2x80x98axe2x80x2xe2x80x99, a length of a straight line from the inner surface evaluation line where a vertical distance between the funnel yoke portion inner surface and the inner surface evaluation line is maximized, to the neck seal inner surface end is xe2x80x98bxe2x80x2xe2x80x99, a formula of 0.20xe2x89xa6bxe2x80x2/axe2x80x2xe2x89xa60.40 is satisfied.
To achieve the above objects, there is also provided a funnel structure of a cathode ray tube having a panel with a fluorescent screen inside thereof, a funnel sealed to the panel in a vacuum state, an electron gun mounted at a neck portion of the funnel and emitting an electron beam toward the fluorescent screen, and a deflection yoke mounted at a yoke portion of the funnel and deflecting the electron beam, wherein provided that a deflection angle is 110xc2x0 or more, a length of an inner surface evaluation line formed by connecting a TOR inner surface end where the funnel yoke portion and the funnel body portion meet and a neck seal inner surface end where the funnel yoke portion and the neck portion meet by a straight line is xe2x80x98axe2x80x2xe2x80x99, a length of a straight line from the inner surface evaluation line where a vertical distance between the funnel yoke portion inner surface and the inner surface evaluation line is maximized, to the neck seal inner surface end is xe2x80x98bxe2x80x2xe2x80x99, a length of a straight line from a point on an inner surface of the funnel yoke portion at which a vertical distance from the inner surface of the funnel yoke portion to the inner surface evaluation line xe2x80x98axe2x80x2xe2x80x99 is maximized to the neck seal end is b1xe2x80x2, a space angle between xe2x80x98bxe2x80x2xe2x80x99 and xe2x80x98b1xe2x80x2xe2x80x99 is xe2x80x98dxe2x80x2xe2x80x99, and an angle formed by a tube axis and the inner surface evaluation line is xe2x80x98cxe2x80x2xe2x80x99, a formula of 0.22xe2x89xa6dxe2x80x2/cxe2x80x2xe2x89xa60.42 is satisfied.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.